Balance sheets of energy and carriers and subcell characteristics in a GaInP/GaAs/Ge tandem solar cell

We developed a straightforward and potentially standard method of accessing the balance sheets of energy and carriers as well as respective subcell photovoltaic properties in multi-junction tandem solar cells by measuring absolute electroluminescence quantum yields. This method was indeed applied to a GaInP/GaAs/Ge 3-junction solar cell for satellite use. The 28.7% efficiency derived as a sum of 15.2% (top), 10.7% (mid) and 2.8% (bottom) of 3 subcells via this method shows good agreement with the measured 27.4% efficiency via an I-V curve under 1-sun illumination at AM0. Moreover, the derived balance sheets of energy and carriers revealed respective subcell contributions of radiative and nonradiative recombination losses, junction loss, thermalization loss, and luminescent coupling, to provide detailed diagnosis and valuable feedback to fabrications.